Examples of a disease for which an operation is performed on a spine include hernia, osteoporosis, and osteoarthritis. Conventionally, an operation method that exhibits a very low invasiveness with the use of a thin needle is employed for hernia and minimal osteoporosis. An operation method for making a large incision in a patient's back is employed for severe osteoporosis and osteoarthritis (for example, refer to Patent Document 1).
In recent years, an operation method for making an incision only in a required minimum part has been widely used even for a disease that conventionally requires a large incision. In this operation method, an operation is performed in such a manner that a cylindrical retractor (also generally referred to as a sleeve) made of metal is inserted into a small incision part, and an endoscope (or an operation microscope) for observing an operation site and forceps or the like for treating the operation site are put in the retractor.
FIG. 1 is a top view of the retractor inserted into the small incision part and the endoscope put in the retractor. FIG. 2 is a cross-sectional view of the retractor and the endoscope. FIG. 3 is a cross-sectional view of the retractor in which the forceps are put.
As illustrated in the drawings, the endoscope 2 is conventionally fixed to an inner wall of the retractor 1. In this case, an oblique mirror, a visible range 3 of which is shifted sideways from the front in a longitudinal direction, is employed for the endoscope 2 so that the operation site that exists in front of a distal end of the retractor 1 can be captured.